The toll tunnel to Sydney's northern beaches is set to cost $1 billion per kilometre

The NSW government’s plan to build a 14-kilometre tunnel connecting Sydney’s inner west to the northern beaches could cost as much as $14 billion – nearly as much as WestConnex at more than twice the length, according to leaked documents.

Premier Gladys Berejiklian announced plans for the tunnel in March, saying the tollway would relieve congestion on the northern beaches and cut travel times from the area to the CBD by up to 40 minutes. The proposed Beaches Link tunnel between Seaforth and Rozelle connects with the $17 billion 33km WestConnex tollway currently under construction. When it was first announced, WestConnex was priced at $10 billion.